It is the intention of the world-wide community to reduce the production of gaseous climate relevant components, such as chlorofluorocarbons (CFC) and carbon dioxide. For the carbon dioxide the worldwide community committed itself to reduce the production within the next decade in the range of about 10 to 15%, depending on the country and its commitment to the Kyoto agreement.
So-called biofuels have the potential to influence the carbon dioxide balance tremendously on a midterm and long-term basis as being a relevant source for renewable primary products, such as wood or related biomass. The estimated cost are expected in the range of 300 Swiss Francs per ton of CO2. These costs are compared to other options taken in the transportation sector quite inexpensive.
Beside natural gas (methane) and hydrogen the biofuels are categorized as potential alternative. On a short-term fuels like RME (bio diesel), ethyl alcohol and bio gas, are available; in mid- to long-term, bio-fuels will be produced according to the already theoretically well-known thermo-chemical processes which take advantage of a catalyst in order to transform a synthesis gas into the desired bio fuel, such as methyl alcohol, synthetic gasoline or diesel, methane, or hydrogen.
A most promising fuel is methane that is supplied actually as fossil gas and which can be replaced under efficient use of synergies between the required infrastructure for both the fossil gas and the biogenic gas by the latter that can be produced by fermentation as well as by thermo-chemical processes.
Unfortunately, one of the most preferred renewable raw material, wood, cannot be transformed into bio gas by fermentation. Therefore, it is a crucial task to provide efficient alternative processes for the synthetic generation of methane from synthesis gas originating from wood gasification processes.
A process known in the art uses wood in a gasification reactor, such as FICFB (Fast Internally Circulation Fluidised Bed), which requires subsequently non-negligible efforts for the pretreatment of the raw synthesis gas in order to allow both effective and efficient synthesis of methane. As far as wood is considered as the renewable raw material, it has to be pointed out that the raw synthesis gas originating from the gasification step, is loaded with considerable amounts of aromatic hydrocarbons and/or C2 components which are known in the prior art to have a negative impact in the subsequent process chain. Therefore, the removal of these aromatic hydrocarbons, such as benzene, toluene and naphthaline (BTN), is acknowledged as being a required process requisite as well as the removal of ammonia NH3 and hydrogen sulfide H2S. Unfortunately, these additional process requisites tend to increase the cost of the synthetic generation of methane from wood and reduce the overall efficiency.
For the reason given above, the crucial pre-requisite for an efficient exploitation of wood for the synthetic generation of methane is to find an optimized concert between the processes of gasification, raw synthesis gas purification and methane generation. Of central importance are the properties of the catalyst required for the generation of methane.